Collar rot in N.F.T. grown tomatoes

A common problem with the nutrient film technique (NFT) is collar rot caused by salts passing up the blocks of growing medium, when these are placed in NFT canals. Soluble salts, especially N salts and phosphates, pass to the surface of the blocks and crystallize on the necks of the plants causing salt burns leading to constriction and restricting water uptake. Hollow stems result, with subsequent wilting and death.